Our research is concerned with basic mechanisms of the regulation and control of cell growth with particular reference to wound healing, but this work also has some applications to the control of neoplasia. The cornea is ideal for such studies because it is avascular and the different cell layers represent populations of isolated cells of all types. We have isolated and purified two fractions of growth factors of biological origin which promote the growth of cells of mesodermal origin. The mesodermal growth factors enhance the development of fibroblasts at the wound edge in organ cultures of corneas. The mesodermal growth factors also preserve the viability of corneas stored by cryopreservation and thus may be useful in clinical corneal grafting. A complex pattern of naturally occurring biological inhibitors of cell division has been found to be produced by corneal fibroblasts in tissue cultures. They block DNA synthesis and possibly mitosis. Some of the inhibitors have been partially isolated from the culture media. Naturally occurring inhibitors of cell growth, produced by living cells, might be especially valuable in the study of natural mechanisms in the regulation of cell growth and also as antitumorigenic agents. The conditions governing the production of these inhibitors of cell division are being studied in detail.